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Hugh Pickens DOT Com (2995471) writes "Hasani Gittens reports that as miraculous as it was that a 16-year-old California boy was able to hitch a ride from San Jose to Hawaii and survive, it isn't the first time a wheel-well stowaway has lived to tell about it. The FAA says that since 1947 there have been 105 people who have tried to surreptitiously travel in plane landing gear — with a survival rate of about 25 percent. But agency adds that the actual numbers are probably higher, as some survivors may have escaped unnoticed, and bodies could fall into the ocean undetected. Except for the occasional happy ending, hiding in the landing gear of a aircraft as it soars miles above the Earth is generally a losing proposition. According to an FAA/Wright State University study titled 'Survival at High Altitudes: Wheel-Well Passengers,' at 20,000 feet the temperature experienced by a stowaway would be -13 F, at 30,000 it would be -45 in the wheel well — and at 40,000 feet, the mercury plunges to a deadly -85 F (PDF). 'You're dealing with an incredibly harsh environment,' says aviation and security expert Anthony Roman. 'Temperatures can reach -50 F, and oxygen levels there are barely sustainable for life.' Even if a strong-bodied individual is lucky enough to stand the cold and the lack of oxygen, there's still the issue of falling out of the plane. 'It's almost impossible not to get thrown out when the gear opens,' says Roman.

So how do the lucky one-in-four survive? The answer, surprisingly, is that a few factors of human physiology are at play: As the aircraft climbs, the body enters a state of hypoxia—that is, it lacks oxygen—and the person passes out. At the same time, the frigid temperatures cause a state of hypothermia, which preserves the nervous system. 'It's similar to a young kid who falls to the bottom of an icy lake," says Roman. "and two hours later he survives, because he was so cold.'"

-85 F is approximately 210 K. Mercury can plunge damn close [springerimages.com] to that as a liquid.

You just need a near-vacuum.

Somewhat ironic that you failed to consider the effect of pressure on phase, especially given this was referencing a high-altitude LOW PRESSURE scenario, but you pedantically cited the freezing point value at standard pressure.

1. Dress warmly. Even if the plane takes off in a tropical location. Make sure to cover exposed body parts - you don't want to pay with eary, fingers, toes or your nose for the trip.
2. Bring oxygen (that's going to be the hard part. Several hours worth of oxygen).
3. Familiarize yourself with various plane types so you don't get crushed by an unsuitable wheel well design.
4. Secure yourself to the plane so you don't get thrown out during landing.

"By the end of the 20th century, most countries used the Celsius scale rather than the Fahrenheit scale. Fahrenheit remains the official scale for the following countries: the Bahamas, Belize, the Cayman Islands, Palau, and the United States and associated territories (Puerto Rico, Guam and the U.S. Virgin Islands)."Yep. Archaic or just retarded?

The US gallon (3.78541 liters) is different than the Imperial gallon (4.54609 liters). Fluid ounces are different too. 128 US fluid oz in a US gallon, 160 imperial fluid ounces in an Imperial gallon. So a US oz is 1.04084 Imp oz.

The problem is the pressure, only 26% at 10km of what you have on ground. Oxygen getting absorbed in your lungs depends on that pressure, less pressure, less oxygen gets to your blood.

No, oxygen getting absorbed into your lungs depends on the partial pressure of oxygen in your breathing gas. Partial pressure is the pressure multiplied by the percentage of the gas in question.

At sea level, the partial pressure of oxygen, ppO2 is 0.21, because the pressure is one atmosphere and the air is 21% oxygen. You can obviously survive just fine on a ppO2 of 0.21. If you're in an environment with 0.26 atm ambient pressure and breathing air, you're getting a ppO2 of 0.26 *0.21 = 0.05 atm. Generally, 0.16 atm is considered the minimum safe ppO2, though that's a pretty conservative number. But 0.05 is not enough to keep you alive. If you're breathing pure O2 at that pressure, though, the ppO2 is 0.26, which is higher than the ppO2 of air at sea level, so you'll be just fine (as long as you avoid freezing to death).

Incidentally, SCUBA divers worry about excessively high ppO2 levels, because oxygen is toxic. Generally, divers try to keep their ppO2 below 1.4 atm, which means that breathing air becomes dangerous at depths greater than 220 feet (of course, at those depths the ppN2 of air is generally already having a huge narcotic effect so diving that deep on air is a bad idea for other reasons). For deeper dives, therefore, divers use gas mixtures with less O2.

Such deep, technical, diving is pretty rare, though. What's very common is diving with air that has been enriched with additional O2, usually to 32% or 36% O2, called nitrox. The purpose of this is to lower ppN2 levels during the dive, to reduce nitrogen absorption by the tissues and therefore increase the amount of bottom time without needing decompression stops to safely offgas the N2. Many divers also think the higher O2 levels make them feel better during and after the dive. However, with 36% O2 (EAN36), ppO2 reaches 1.4 atm at only 128 feet so divers breathing nitrox have to be careful to stay shallower. Smart Nitrox divers test their breathing gas O2 percentage before every dive and calculate a floor below which they must not go.

For example Mount Everest climbers, if they just ran from 0m to top of Everest they would pass out, extra oxygen or no.

The top of Mount Everest is about 0.33 atm, which means a 100% O2 mixture would provide them with more oxygen than they get at sea level. The reason they have to acclimate first is that carrying enough O2 to breathe 100% O2 is impractical. It would require carrying thousands of cubic feet of compressed gas. By acclimating themselves they increase their bodies' ability to utilize lower ppO2 levels. Depending on their fitness levels and degree of acclimatization, they may be able to get to a point where they don't require supplemental oxygen. Most, though, will need some.

Actually, terminal SPEED is the result of drag forces that scale like bv^2 opposing motion. The horizontal velocity component v_0 decays to zero like, lessee, v_x(t) = mv_0/(b v_0 t + m), just as the vertical component approaches the value where drag force balances gravitation like a hyperbolic tangent with a similar characteristic time. The real question is how long one is in the air relative to the drag and mass, that is, if dimensionless b v_0 t/m >> 1. A small person wearing a big puffy jacket (small m, large b) might do much better than a big guy wearing a tight wetsuit. With a v_0 on the order of hundreds of meters per second and greater than terminal speed, one of the times it is actually better to fall from a larger height rather than a smaller one to allow initial speed to decay to terminal speed.

There are a number of cases on record of people falling out of moving airplanes (presumably travelling at speeds order of 300 to 800 kph, well above terminal speed) who survived, usually by falling into deep snow, soft plowed fields, just the right patch of springy trees. A VERY few weren't even terribly injured. And you are dead right -- water, an incompressible fluid, is literally "as hard as concrete" when struck at high speed. Because it isn't compressible, the collision has to literally move the quite massive water out of the way. People who jump from bridges don't always or even generally drown -- they break bones, rupture their body cavity, suffer massive internal brain trauma. There is an amusing, not-quite-tongue-in-cheek section in the Worst Case Scenario Survival Guide on surviving a fall out of a plane several kilometers high over water. Falling bluff (maximize b), turning vertical at the last moment, enter feet first and streamlined and keep those butt-cheeks clenched as we don't want to explode our intestines via a power enema.

With luck one breaks ones legs, pops a few disks, remains conscious, floats back to the surface in time to breathe, and can then stay afloat with broken legs and internal injuries until somebody pulls you out of the water and gets you to medical care. I'm sure one "can" learn to enter the water perfectly enough to do better than this -- cliff divers manage it at a significant fraction of terminal speed -- but it's one of those experiences most of us would be better off avoiding...:-)